That instead of one poorly managed understaffed silo full of trolls and abusers you have 2000 poorly managed, even more understaffed systems with 2000 different approaches to moderation and content doesn't make anything easier or fixed for people who use Twitter today.
It is the same like we had federated chat with Jabber for 20 years now - and nobody uses it. The best implementations of it ended being the nonfederated ones - like Google Talk or I believe Whatsapp used that protocol. And apart from nerds and some engineers literally has no clue that something like XMPP even exists.
People don't care about the technology, they care where they want to communicate with their friends and network.
The Twitter issues are first and foremost human, business, management and social problems, not something you can throw some network protocols and technology at and declare it solved.